There are quite a few people on the reddit r/keto channel who have been on a keto diet for 10 years or longer, many of them on a much stricter keto diet than we are following.
Once we reach our goal weights (at least another 20 pounds for me), we may relax it further, although many people report that after following a keto diet for a long time, their body doesn't react well when going back to a SAD diet.
Currently I'm aiming for 40-50 carbs a day and 1000-1200 calories, my 7 day average is 912 calories and 41 carbs, with 59% of calories from fat, 24% from protein, and 18% from carbs. (Doesn't add up to 100 due to rounding issues, I assume.) I'm using Nutritionix for tracking, and working on a full review of it.